1. Field of the Invention
The present invention relates to an angle adjusting device so-called a gonio-stage or swivel-stage.
2. Description of the Related Art
One of the prior art documents regarding the angle adjusting device of the invention is JP-A-2000-230548 (FIG. 1, FIG. 10). This publication discloses a biaxial angle adjusting device. In a first embodiment of this device, a lower stage structure and an upper stage structure are substantially the same. In each stage, the device has a pedestal, U-shaped in cross section, having a bottom wall and both side walls. The upper edge of both side walls for this pedestal is formed like a circular arc, and a guide member having an arcuate shape is fixed on a vertical flat outer face (setting plane) along the upper edge thereof. This guide member is fixed to the side wall by a screw from the outside. An arcuate groove (track) is formed on the upper and lower faces of the guide member.
Moreover, the device comprises an oscillation body in each stage. This oscillation body comprises an oscillation table having an upper wall and both side walls, and U-shaped in cross section, and a transit block fixed to an inner face of both side walls for this oscillation table. Each transit block has an endless circulation passage, and balls are arranged in this endless circulation passage. A part of this endless circulation passage faces a track of the guide member, and the balls located between them roll while moving along the track of the transit block.
The device further has moving means. This moving means moves the oscillation body along the arcuate track to adjust the angular position of the oscillation body around an oscillation axis (axis passing through the center of radius of curvature for the track). This moving means comprises a motor provided in the oscillation table and an arcuate rack meshing with a pinion in the first embodiment of the above publication, as shown in FIG. 1. This rack is fixed near the upper edge of the inner face of both side walls for the pedestal. Along with the rotation of the motor, the oscillation body is moved along the track via the engagement of the pinion and the rack.
In a fourth embodiment of the publication as shown in FIG. 10, the moving means in the lower stage is different from that of the first embodiment. The moving means in the lower stage comprises a motor provided in the pedestal, a ball screw mechanism linked with this motor, a first movement body that is linearly moved horizontally by the ball screw mechanism, and a second movement body slidably provided vertically on this first movement body. The oscillation table is rotatably linked to the second movement body. In this embodiment, the first movement body is moved horizontally via the ball screw mechanism along with the rotation of the motor, in which this horizontal movement is converted via the second movement body into the movement of the oscillation table along the track.
A device of JP-A-2001-99150 (FIG. 2, FIG. 4), like the above publication, comprises a pedestal, one pair of arcuate guide members fixed to this pedestal, an oscillation body being moved along the track of the guide members, and moving means for moving the oscillation body to adjust the angular position of the oscillation body around an oscillation axis (axis passing through the center of radius of curvature for the arcuate track). A convex portion is formed in the center of the pedestal, and serves as a first setting plane where both side faces of this convex portion are vertical. Also, an upper face adjacent to the convex portion is an arcuate face, serving as a second setting plane. By the way, one side face of the guide member is a first reference plane, flat, and an arcuate groove serving as the track is formed on the other side face. Moreover, a lower face of the guide member is a second reference plane serving as an arcuate face. The guide member is fixed to the pedestal by screw toward the second setting plane in a state where the flat first reference plane of the guide member is in contact with the first setting plane for the pedestal and the second reference plane of arcuate face is in contact with the second setting plane.
The moving means of the device of JP-A-2001-99150 comprises a motor provided in the pedestal, a worm that is rotated by this motor, and a gear portion formed on the oscillation body and meshing with the worm. Along with the rotation of the motor, the oscillation body is rotated via the engagement of the worm and the gear portion.
In recent years, there is a demand for making the fine angular adjustment at high precision. However, with the conventional angle adjusting device comprising the device of the above publication, this demand was not met with. The reason will be detailed below.
In the device of JP-A-2000-230548, since the guide member is fixed by screws in a state where the arcuate flat reference plane is in contact with the flat setting plane of the pedestal, the arcuate guide member is distorted at the time of tightening the screw, so that the roundness of the track for the guide member is degraded. Also, in the device of JP-A-2001-99150, since the second reference plane of the guide member is aligned with the circular face of the second setting plane in the pedestal, if the roundness of the circular arc of the second setting plane is low, or the second setting plane and the second reference plane have slightly different radius of curvature for the circular arc, the guide member is distorted and the roundness of the track for the guide member is degraded, so that the precision of the angular position adjustment is degraded.
In the first embodiment of JP-A-2000-230548, the rack and the pinion are provided in each of the oscillation body and the pedestal. In the fourth embodiment, the customized ball screw mechanism is built into the pedestal. Also, in the device of JP-A-2001-99150, the worm and the gear portion are provided in the pedestal and the oscillation body. In these structures, the angular position adjustment did not have high precision due to looseness of an engagement portion exposed outside.